package org.apache.lucene.search;

/**
 * Copyright 2005 The Apache Software Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import org.apache.lucene.index.IndexReader;
import org.apache.lucene.search.Explanation;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.Scorer;
import org.apache.lucene.search.Searcher;
import org.apache.lucene.search.Similarity;
import org.apache.lucene.search.Weight;
import org.apache.lucene.util.ToStringUtils;

/**
 * A query that matches all documents.
 * 
 * @author John Wang
 */
public class MatchAllDocsQuery extends Query {

    public MatchAllDocsQuery() {
    }

    private class MatchAllScorer extends Scorer {

        final IndexReader reader;
        int id;
        final int maxId;
        final float score;

        MatchAllScorer(IndexReader reader, Similarity similarity, Weight w) {
            super(similarity);
            this.reader = reader;
            id = -1;
            maxId = reader.maxDoc() - 1;
            score = w.getValue();
        }

        public Explanation explain(int doc) {
            return null; // not called... see MatchAllDocsWeight.explain()
        }

        public int doc() {
            return id;
        }

        public boolean next() {
            while (id < maxId) {
                id++;
                if (!reader.isDeleted(id)) {
                    return true;
                }
            }
            return false;
        }

        public float score() {
            return score;
        }

        public boolean skipTo(int target) {
            id = target - 1;
            return next();
        }

    }

    private class MatchAllDocsWeight implements Weight {
        private Searcher searcher;
        private float queryWeight;
        private float queryNorm;

        public MatchAllDocsWeight(Searcher searcher) {
            this.searcher = searcher;
        }

        public String toString() {
            return "weight(" + MatchAllDocsQuery.this + ")";
        }

        public Query getQuery() {
            return MatchAllDocsQuery.this;
        }

        public float getValue() {
            return queryWeight;
        }

        public float sumOfSquaredWeights() {
            queryWeight = getBoost();
            return queryWeight * queryWeight;
        }

        public void normalize(float queryNorm) {
            this.queryNorm = queryNorm;
            queryWeight *= this.queryNorm;
        }

        public Scorer scorer(IndexReader reader) {
            return new MatchAllScorer(reader, getSimilarity(searcher), this);
        }

        public Explanation explain(IndexReader reader, int doc) {
            // explain query weight
            Explanation queryExpl = new Explanation();
            queryExpl.setDescription("MatchAllDocsQuery, product of:");
            queryExpl.setValue(getValue());
            if (getBoost() != 1.0f) {
                queryExpl.addDetail(new Explanation(getBoost(), "boost"));
            }
            queryExpl.addDetail(new Explanation(queryNorm, "queryNorm"));

            return queryExpl;
        }
    }

    protected Weight createWeight(Searcher searcher) {
        return new MatchAllDocsWeight(searcher);
    }

    public String toString(String field) {
        StringBuffer buffer = new StringBuffer();
        buffer.append("MatchAllDocsQuery");
        buffer.append(ToStringUtils.boost(getBoost()));
        return buffer.toString();
    }

    public boolean equals(Object o) {
        if (!(o instanceof MatchAllDocsQuery))
            return false;
        MatchAllDocsQuery other = (MatchAllDocsQuery) o;
        return this.getBoost() == other.getBoost();
    }

    public int hashCode() {
        return Float.floatToIntBits(getBoost()) ^ 0x1AA71190;
    }
}
